How to fix ASP.NET Web Forms App: “Hmm… can’t reach this page” error when running project in Visual Studio

Thank you for reaching out.

This error means the browser can’t connect to IIS Express even though the ASP.NET Web Forms app compiles successfully. Since you already tried deleting the .vs folder, rebuilding, and checking the port and start page, the problem is most likely in how Visual Studio is recognizing or hosting the project.

1. Confirm the project type
If you created the Web Forms project manually, Visual Studio might not treat it as a web application.
Fix

1. In Solution Explorer, right-click the project → Unload Project → Edit .csproj
2. Inside the first , make sure these lines exist:

      <ProjectTypeGuids>
       {349c5851-65df-11da-9384-00065b846f21};
      {fae04ec0-301f-11d3-bf4b-00c04f79efbc} 
      </ProjectTypeGuids> 
      <OutputType>Library</OutputType>
   

3. Save, reload the project, rebuild, and run again.
   Without those GUIDs, Visual Studio will compile the code but not launch IIS Express to host it, which produces the “can’t reach page” message.

2. Recreate IIS Express configuration
Instead of deleting files again, reset IIS Express cleanly so Visual Studio rebuilds its configuration.

1. Close Visual Studio.
2. Rename (do not delete):
   • .vs → .vs_backup in your project folder
     • C:\Users\<you>\Documents\IISExpress → IISExpress_backup
3. Re-open the project.
4. Open Project → Properties → Web, choose Create Virtual Directory, save, and run.
   This forces Visual Studio to regenerate a fresh applicationhost.config with correct bindings.

3. Switch to HTTP temporarily
If your project URL begins with https://localhost:xxxx, change it to http://localhost:xxxx in Project → Properties → Web and run again.
SSL certificate mismatches or expired developer certs can prevent IIS Express from starting.

4. Verify the binding in applicationhost.config
Open
C:\Users\<you>\Documents\IISExpress\config\applicationhost.config
and look under \ for your project entry:

<binding protocol="http" bindingInformation="*:12345:localhost" />

Confirm that the port matches the one in your project properties and that the physicalPath points to your project folder.

5. Check for port conflicts
Run in an elevated Command Prompt:

netstat -ano | findstr :12345

Replace 12345 with your port. If another process is using it, stop that process or choose a different port in Project → Properties → Web.

6. Optional steps if it still fails

• In Visual Studio Installer, open Modify → Individual Components and ensure ASP.NET and Web Development workload is installed.
• If using HTTPS, reset local certificates:

dotnet dev-certs https --clean dotnet dev-certs https --trust 

Let me know if you need any further help with this. We'll be happy to assist.

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